22 Artifact & Troubleshooting Practice Questions & Answers

1. 1. A 12-lead tracing shows a very fine, uniform, rapid oscillation of identical amplitude and perfectly even spacing that thickens the baseline into a fuzzy band; it is present in every lead and the P-QRS-T complexes are still identifiable through it. Which artifact is this?

   • A.Wandering baseline
   • B.Somatic (muscle) tremor artifact
   • C.Interrupted baseline from a detached electrode
   • D.AC (60-cycle) electrical interference✓ Answer

   The defining feature of AC interference is uniformity: the oscillations are identical in height and evenly spaced (60 cycles per second in the U.S.) because they come from a steady external power-line field rather than from the patient. Somatic tremor, by contrast, is irregular and varies in height and spacing, and wandering baseline is a slow smooth drift, not a fine rapid oscillation.

   Source: NHA CET Test Plan, EKG Acquisition — knowledge statement: causes and types of artifacts (wandering baseline, somatic tremor, AC interference)Report a problem with this question

2. 2. An EKG shows erratic, jagged, spiky deflections of clearly varying height and irregular spacing superimposed on the baseline; the patient is tense, in pain, and keeps shifting on the table. Which artifact best matches this appearance?

   • A.Somatic (muscle) tremor artifact✓ Answer
   • B.Interrupted baseline from a fractured lead wire
   • C.Wandering baseline
   • D.AC (60-cycle) electrical interference

   Skeletal muscle generates its own electrical activity, so voluntary or involuntary movement produces spikes that are irregular in both amplitude and timing — the opposite of the even, identical oscillation of AC interference. Recognizing the irregularity is what separates somatic tremor from 60-cycle interference on a described tracing.

   Source: NHA CET Test Plan — somatic tremor artifact recognitionReport a problem with this question

3. 3. During a resting 12-lead, the isoelectric line slowly and smoothly rises and falls across the paper in a low-frequency undulation that rises and falls in time with the patient's breathing; the waveforms themselves stay sharp and recognizable but ride up and down. Which artifact is present?

   • A.Somatic (muscle) tremor artifact
   • B.Wandering baseline✓ Answer
   • C.AC (60-cycle) electrical interference
   • D.Complete signal loss in one lead group

   A slow, smooth, low-frequency drift of the baseline that tracks respiration is the classic description of wandering baseline, which arises from mechanical changes in electrode-to-skin contact rather than from electrical noise. Because the complexes themselves remain sharp, the problem is contact and movement, not signal quality at high frequency.

   Source: NHA CET Test Plan — wandering baseline recognitionReport a problem with this question

4. 4. A technician uses electrodes from a pouch that was opened several days earlier, and applies them to a patient's arms without removing the body lotion the patient had just applied. The resulting tracing shows a slowly drifting, swaying baseline in the limb leads. What is the most likely cause?

   • A.The lead wires are crossing the machine's power cord
   • B.The RA and LA electrodes have been reversed
   • C.Dried-out electrode gel plus skin oils and lotion preventing firm, conductive electrode contact✓ Answer
   • D.The machine is plugged into an ungrounded outlet

   Wandering baseline is a contact problem: dried or expired gel and an oily, lotioned surface both raise impedance and let the electrode shift, so the recorded reference level drifts. An ungrounded machine or crossed power cord would produce uniform 60-cycle interference instead, and reversed arm electrodes change waveform polarity rather than causing drift.

   Source: NHA CET Test Plan and 2.G — skin preparation and causes of wandering baselineReport a problem with this question

5. 5. A tracing is rejected because of a slow, drifting baseline. Which corrective sequence best addresses this artifact?

   • A.Re-prep the skin (clean, dry it completely, clip hair, gently abrade), apply fresh in-date electrodes, leave slack in the lead wires routed along the body contour, and repeat the tracing✓ Answer
   • B.Turn on the 60-Hz notch filter and reprint the same tracing
   • C.Change the paper speed to 50 mm/sec
   • D.Reverse the RA and LA electrodes to cancel the drift

   Because wandering baseline comes from unstable electrode-skin contact and wire tension, the fix is mechanical: restore a clean, dry, low-impedance site, use moist in-date gel, and relieve pull on the wires, then re-record. Filters, lead swaps, and speed changes do not restore contact and would only mask or distort the tracing.

   Source: NHA CET Test Plan — methods to resolve artifacts; skin preparationReport a problem with this question

6. 6. A patient in a cold exam room is visibly shivering, and the tracing shows irregular jagged spikes of varying height across all limb leads. What should the technician do first?

   • A.Move the machine away from the wall and unplug nearby equipment
   • B.Enable the 60-Hz AC filter and accept the tracing as it prints
   • C.Switch to half standardization so the spikes look smaller
   • D.Cover the patient with a blanket and warm the room, reassure the patient, support the arms and legs on the table, then repeat the tracing✓ Answer

   Shivering is muscle activity, so the artifact stops only when the muscle activity stops — warmth, reassurance, and supported limbs remove the source. Filtering or reducing gain merely hides or shrinks the noise while still leaving a non-diagnostic tracing, and moving electrical equipment addresses AC interference, a different artifact.

   Source: NHA CET Test Plan and 2.G — patient positioning and resolution of somatic tremorReport a problem with this question

7. 7. A patient with a resting tremor from Parkinson's disease cannot hold the arms and legs still, and the limb leads are filled with jagged muscle artifact. Which technique is most appropriate to obtain a diagnostic tracing?

   • A.Reverse the arm electrodes so the tremor cancels out
   • B.Move the limb electrodes proximally toward the torso (upper arms/shoulders and hips) and have the patient place the hands palm-up under the thighs, then repeat the tracing✓ Answer
   • C.Leave the electrodes on the wrists and ankles and reduce the gain to 5 mm/mV
   • D.Record only the six chest leads and omit the limb leads

   Tremor amplitude is greatest at the distal extremities, so moving the limb electrodes proximally and immobilizing the hands under the thighs records from a comparatively still area and greatly reduces the muscle signal. Lowering the gain or dropping leads would falsify amplitude or leave the tracing incomplete, and swapping electrodes creates a lead reversal.

   Source: NHA CET Test Plan and 2.G — special considerations in positioning and artifact resolutionReport a problem with this question

8. 8. Every lead of a tracing shows the same fine, evenly spaced fuzzy thickening of the baseline. Which finding in the room most likely explains it?

   • A.The patient took a deep breath just before the recording
   • B.The electrode gel has dried out
   • C.The LL electrode was placed over a bony prominence
   • D.The patient cable is lying across the machine's power cord next to a running IV pump✓ Answer

   AC interference is induced when the patient cable picks up the alternating field radiated by power cords and energized devices, which is why crossing the power cord beside running equipment is the classic source. Dried gel, respiration, and a bony electrode site cause drift or poor contact, not a uniform high-frequency oscillation.

   Source: NHA CET Test Plan — causes of AC (electrical) interferenceReport a problem with this question

9. 9. A tracing is spoiled by uniform 60-cycle interference in all leads. What is the correct way to resolve it?

   • A.Move or unplug nearby electrical equipment, uncross and separate the lead wires from the power cord, confirm the machine is in a grounded three-prong outlet, and repeat the tracing✓ Answer
   • B.Increase the gain to 20 mm/mV so the complexes stand out above the noise
   • C.Ask the patient to hold their breath during the recording
   • D.Apply the 60-Hz notch filter and release the tracing without changing anything else

   The interference is being induced by an external source, so eliminating or separating from that source and verifying the ground removes the artifact at its origin. The notch filter is only a secondary measure and is not a substitute for correcting the cause; breath-holding addresses baseline drift, and raising the gain amplifies the noise along with the signal.

   Source: NHA CET Test Plan and 2.G — equipment/electrical safety and methods to resolve artifactsReport a problem with this question

10. 10. On a 12-lead recording, lead III prints as a completely flat line while leads I, II, aVR, aVL, aVF and all six chest leads show normal sinus complexes at 78 beats per minute; the patient is sitting up talking. What does this most likely represent?

    • A.Loss of contact at an electrode or lead wire feeding lead III — reattach or replace the electrode, check the cable connection, and repeat the tracing✓ Answer
    • B.Asystole — begin CPR immediately
    • C.Fine ventricular fibrillation
    • D.Somatic tremor artifact in lead III

    Asystole is a whole-heart event, so it must be flat in every lead and the patient would be unresponsive and pulseless; a flat line in one lead with normal complexes elsewhere can only be an acquisition failure at the electrode, wire, or cable serving that lead. The correct response is to restore the connection and re-record, not to treat a rhythm the patient does not have.

    Source: NHA CET Test Plan and 2.G — lead placement and troubleshooting; interrupted baselineReport a problem with this question

11. 11. Heavy artifact appears only in leads II, III and aVF, while leads I, aVR, aVL and all chest leads are clean. Which electrode is the most likely source of the problem?

    • A.The left arm (LA) electrode
    • B.The right arm (RA) electrode
    • C.The V4 chest electrode
    • D.The left leg (LL) electrode✓ Answer

    Each limb lead is derived from a specific pair of electrodes, and leads II, III and aVF are the three that all share the left leg electrode, so artifact confined to exactly that group localizes the fault to LL. Applying the same logic, noise in I, II and aVR points to RA, noise in I, III and aVL points to LA, and noise in a single V lead points to that chest electrode.

    Source: NHA CET Test Plan — lead placement and troubleshooting (electrode-to-lead relationships)Report a problem with this question

12. 12. A monitored patient's telemetry suddenly shows a chaotic, wide, rapid pattern that resembles ventricular tachycardia in one lead only; the underlying sinus QRS complexes can still be seen marching through at the same R-R interval as before, the other leads are clean, and the patient is sitting up brushing their teeth. What is the appropriate action?

    • A.Print and mount the strip and continue the shift without further action
    • B.Increase the paper speed to 50 mm/sec so the rhythm is easier to read
    • C.Immediately check the patient's responsiveness and pulse; with an alert patient, a pulse, and sinus complexes marching through, treat it as motion artifact — correct the cause and obtain a clean tracing✓ Answer
    • D.Document the strip as ventricular tachycardia and place it in the chart

    The rule is treat the patient, not the monitor: assessment comes first, and an awake patient with a pulse cannot be in ventricular tachycardia that is hemodynamically collapsing. Seeing the original sinus QRS complexes continue at the unchanged R-R interval through the chaos, in only one lead while the others are clean, is the signature of artifact rather than a true arrhythmia, and a rhythm must never be documented from an uncorrected artifact-laden strip.

    Source: NHA CET Test Plan and coordinated patient care — distinguishing artifact from true arrhythmiaReport a problem with this question

13. 13. A 12-lead on an asymptomatic adult shows a globally inverted lead I (negative P wave, negative QRS and negative T wave), an upright aVR that looks like a normal lead I, and normal R-wave progression from V1 through V6. What is the most likely explanation?

    • A.AC interference in the limb leads
    • B.The LA and RA electrodes have been reversed✓ Answer
    • C.An acute anterolateral myocardial infarction
    • D.Dextrocardia

    Swapping the two arm electrodes reverses the polarity of lead I and makes aVR mirror a normal lead I, but it cannot affect the chest electrodes, so R-wave progression stays normal. Dextrocardia would produce the same limb-lead picture plus reversed or regressing R waves across the precordium, and that preserved precordial progression is the discriminator — this is a technical error to be corrected, not a cardiac finding.

    Source: NHA CET Test Plan and 2.F — lead placement and troubleshooting; limb lead reversal recognitionReport a problem with this question

14. 14. A tracing shows lead II as an almost perfectly flat, near-zero line while leads I and III display normal complexes and the patient is alert with a strong radial pulse. What is the most likely cause?

    • A.Reversal of the LA and LL electrodes
    • B.Reversal of the RA and RL (neutral/ground) electrodes✓ Answer
    • C.60-cycle interference limited to lead II
    • D.True asystole confined to that lead

    Lead II is recorded between the right arm and the left leg, so if RA is swapped with the neutral RL electrode the two inputs sit on the same leg and the potential difference is essentially zero, printing a flat line. Asystole cannot be confined to one lead, LA/LL reversal inverts lead III instead, and AC interference thickens rather than flattens the baseline.

    Source: NHA CET Test Plan — lead placement and troubleshooting; reversals involving the neutral (RL) electrodeReport a problem with this question

15. 15. After printing a 12-lead, the technician recognizes a limb lead reversal. What is the correct action?

    • A.Reposition the electrodes correctly and record a completely new tracing✓ Answer
    • B.Hand-write corrected lead labels on the printout and submit it
    • C.Ask the interpreting provider to mentally flip the affected leads
    • D.Cut the strip apart and remount the leads in the corrected order

    A reversed tracing is not a labeling problem but a recording of the wrong electrical vectors, so relabeling, mental correction, or remounting all leave inaccurate waveform data in the medical record. The only defensible remedy is to correct the electrode positions and repeat the acquisition; a tracing must never be annotated, edited, or trimmed to appear correct.

    Source: NHA CET Test Plan and 2.H — elements of a complete EKG tracing and mountingReport a problem with this question

16. 16. An asymptomatic adult's tracing shows an rSr' pattern with a negative P wave in V1 and V2, T-wave inversion in those leads, and poor R-wave progression. The technician notices the V1 and V2 electrodes were placed in the 2nd intercostal space. What should be done?

    • A.Recognize that V1 and V2 are too high, move them to the 4th intercostal space at the right and left sternal borders, and repeat the tracing✓ Answer
    • B.Report the tracing as an acute anteroseptal infarction
    • C.Enable the muscle (artifact) filter and reprint
    • D.Conclude the patient has dextrocardia and reverse the arm electrodes

    Placing V1 and V2 one or two interspaces too high is the most common precordial error and reproducibly creates a negative P wave, an rSr' incomplete-right-bundle look, T inversion and poor R progression that mimic pathology. Because the finding is generated by placement rather than by the heart, the answer is to correct the landmark — V1 at the 4th intercostal space right sternal border and V2 at the 4th intercostal space left sternal border — and re-record; the technician acquires and reports, and does not diagnose infarction.

    Source: NHA CET Test Plan — precordial electrode placement landmarks and troubleshootingReport a problem with this question

17. 17. After correctly placing V4 in the 5th intercostal space at the midclavicular line, where do V5 and V6 belong?

    • A.Level with V2 in the 4th intercostal space, lateral to the sternum
    • B.Following the 5th rib upward, V5 at the anterior axillary line and V6 at the posterior axillary line
    • C.In the 6th intercostal space at the anterior and midaxillary lines
    • D.Horizontally level with V4 — V5 at the anterior axillary line and V6 at the midaxillary line✓ Answer

    V5 and V6 are defined by the horizontal plane of V4, not by an intercostal space, so they must sit on the same level as V4 at the anterior axillary and midaxillary lines respectively. Letting them ride up along the rib line lowers recorded amplitude and distorts the apparent axis, producing a non-comparable tracing on serial studies.

    Source: NHA CET Test Plan — standard precordial electrode landmarks (V4–V6 horizontal plane)Report a problem with this question

18. 18. Before releasing a resting 12-lead as diagnostic quality, the technician verifies the machine settings. Which paper speed and gain are the standard settings that should be printed on the tracing?

    • A.25 mm/sec and 5 mm/mV
    • B.25 mm/sec and 10 mm/mV✓ Answer
    • C.10 mm/sec and 25 mm/mV
    • D.50 mm/sec and 20 mm/mV

    The universally standardized recording conventions are a paper speed of 25 mm/sec and a sensitivity of 10 mm/mV, which is what makes one small 1-mm box equal 0.04 second horizontally and 0.1 mV vertically and one large 5-mm box equal 0.20 second. Any departure from these settings changes apparent width or amplitude and must be documented on the tracing.

    Source: NHA CET Test Plan, verify EKG machine settings: speed, gain and knowledge statement on graph paper unitsReport a problem with this question

19. 19. A technician checks the calibration pulse at the beginning of a tracing recorded at standard settings. A correct standardization mark should be about how tall and how wide?

    • A.20 mm tall and about 0.40 second wide
    • B.5 mm tall and 0.04 second wide
    • C.1 mm tall and about 0.20 second wide
    • D.10 mm tall and about 0.20 second wide✓ Answer

    The standardization pulse is a 1-mV calibration signal, and at the standard sensitivity of 10 mm/mV it must deflect exactly 10 mm; at 25 mm/sec its plateau spans about 0.20 second. A mark that is the wrong height tells you the gain is not standard, and a rounded or sloping mark indicates a machine problem that must be corrected before the tracing can be trusted.

    Source: NHA CET Test Plan and 2.F — machine settings and elements of a complete EKG tracing (standardization mark)Report a problem with this question

20. 20. The QRS complexes on a tracing are so tall that they overlap and overwrite the adjacent lead channels, making the tracing unreadable. What is the appropriate technician response?

    • A.Turn on the 40-Hz muscle filter to shrink the complexes
    • B.Move the V4 through V6 electrodes lower on the chest to reduce voltage
    • C.Switch to half standardization (5 mm/mV) and document the change on the tracing✓ Answer
    • D.Increase the paper speed to 50 mm/sec and note it on the tracing

    Half standardization halves the recorded amplitude so oversized complexes fit within their channel, and it must be documented because every millimeter of height on that tracing now represents twice the voltage it normally would. Faster paper speed changes width rather than height, the muscle filter is for tremor noise and would distort the waveform, and moving chest electrodes off their landmarks falsifies the recording.

    Source: NHA CET Test Plan and 2.F — machine settings (half/double standardization) and documentation of deviationsReport a problem with this question

21. 21. Which skin-preparation practice best prevents artifact when applying electrodes?

    • A.Clean the site to remove oils and lotion and let it dry completely before applying the electrode✓ Answer
    • B.Apply the electrode while the site is still wet with alcohol so that it conducts better
    • C.Choose bony prominences such as the clavicle or sternum because they hold the electrode more firmly
    • D.Use a lotion or cream under the electrode to improve adhesion to dry skin

    Oils, lotion and residual moisture all raise skin impedance and undermine the adhesive, which is the leading pathway to wandering baseline and dropout, so the site must be cleaned and then dried completely. Electrodes belong on flat fleshy areas rather than bone, and adding lotion or applying to a wet surface makes contact worse, not better.

    Source: NHA CET Test Plan — prepare skin for electrode placementReport a problem with this question

22. 22. A completed 12-lead shows heavy artifact in leads I, II and aVR while the rest of the tracing is clean. The patient is still in the room. What is the correct response sequence?

    • A.Discard the tracing and reschedule the patient for another day
    • B.Turn on every available filter, reprint, and submit whatever prints
    • C.Draw arrows on the strip, write "artifact" beside the affected leads, and submit it
    • D.Determine which leads are affected, trace the fault to the electrode they share (the right arm electrode), correct the electrode and connection, and record a new complete tracing before the patient leaves✓ Answer

    Leads I, II and aVR are exactly the three leads that share the right arm electrode, so the affected group localizes the faulty electrode and tells the technician what to fix. Tracing quality must be verified while the patient is still present, and an artifact-laden tracing is corrected and repeated rather than annotated, filtered into submission, or deferred, because no interpretation may be made from a non-diagnostic recording.

    Source: NHA CET Test Plan and 2.G — verify all leads recorded / elements of a complete tracing and methods to resolve artifactsReport a problem with this question

Practice questions based on the NHA Certified EKG Technician (CET) test plan, the standard 12-lead electrode positions defined by anatomical landmark, and durable cardiac electrophysiology. CET is a mark of the National Healthcareer Association; this site is not affiliated with or endorsed by NHA. An EKG technician records tracings and does not diagnose. Always follow your facility's policies, your state's scope of practice, and the direction of the ordering provider. About the CET exam →